This invention relates to an electrically driven and electrically heated endodontic syringe for extruding heated thermoplastic material through a needle into a tooth root canal cavity.
Historically, dental root canal cavities have long been filled with gutta percha, a gum obtained by boiling the sap of certain species of trees particularly native to Borneo, New Guinea, and Malaya. The procedure has for a long time been a hand operation in which slender needle-shaped "points" of gutta percha are pushed and packed into the root canal cavity by hand tools.
More recently there have been some advances in the art, particularly in terms of mechanization. While some synthetic materials for this use have been devised, gutta percha remains the standard and favorite. It is desirable, in order to do the best job of filling any cavity, to fill it with liquid rather than to pack it with a solid. With gutta percha, this presents problems. It must be heated to approximately 230.degree. F. in order to flow freely into fine spaces or through a fine orifice. In order to mechanize the extrusion of gutta percha through a needle and into a root canal cavity, not only must the body or reservoir of gutta percha be heated, but the gutta percha must also be maintained at elevated temperature through the length of the needle.
U.S. Pat. No. 4,265,618 to Herskovitz et al discloses one apparatus in which this problem has been addressed. In Herskovitz et al, a hand-held syringe includes a cylindrical electrical heater into which a rod of gutta percha is placed. A needle of copper or silver extends from the heater body. The gutta percha is heated within the cylindrical heater, then pushed out of the heater, by means of a manual plunger rod, through the copper or silver needle. The needle, by virtue of its high thermal conductivity, is said to conduct enough heat from the heater body to keep the gutta percha in a fluid condition throughout the length of the needle. Copper or silver was considered necessary in Herskovitz et al because of the required length of the needle, and the needle in turn is of such required length to enable the user to put proper bends in it for use. It is not clear, but it appears that in the use of this device, when the procedure is completed the user must somehow flush the needle of remaining gutta percha, perhaps by pushing boiling water through it, to prevent its being permanently clogged.